$ C = \left[\begin{array}{rrr}2 & 0 & 1 \\ 1 & 1 & 0 \\ 1 & 2 & 2\end{array}\right]$ What is $ C^{-1}$ ?
Answer: $ = \left[\begin{array}{rrr}\frac{2}{5} & \frac{2}{5} & -\frac{1}{5} \\ -\frac{2}{5} & \frac{3}{5} & \frac{1}{5} \\ \frac{1}{5} & -\frac{4}{5} & \frac{2}{5}\end{array}\right]$